You're right that South Korea is "first world" in modern usage.
"First world" once referred to just the US, UK, and parts of Western Europe; essentially just the NATO allies. I think some people still use that outdated interpretation, possibly including the original poster. Time for an update.
"Third world" just means non-aligned, when talking about the US versus Russia. But I agree with you that it's needlessly pejorative here.

It looks like it was built out for him by Air Cargo, and possibly managed by them as well, but the registration shows that it's owned by a Utah bank trustee, which I would expect is a proxy for this guy. I do think he actually owns this beast.
https://registry.faa.gov/AircraftInquiry/NNum_Results.aspx?NNumbertxt=767CJ

Depending on your political leaning you can select among these alternative sources for essentially the same story. You're welcome.
https://abcnews.go.com/Politics/16-accidentally-blown-belgian-air-force-mechanic/story?id=58562311
https://www.telegraph.co.uk/news/2018/10/14/belgian-mechanic-accidentally-destroys-f-16-fighter-jet-cannon/
http://www.f-16.net/f-16-news-article5127.html
https://www.rt.com/news/441017-f-16-aircraft-explodes-belgium/
https://twitter.com/BeAirForce/status/1050394683007008768
https://aviation-safety.net/wikibase/wiki.php?id=216189
https://www.airforcetimes.com/news/your-air-force/2018/10/16/belgian-air-force-mechanic-opens-fire-by-mistake-blows-up-another-f-16/
https://fox61.com/2018/10/15/belgian-f16-destroyed-due-to-accidental-cannon-firing/

10th paragraph.
"The researchers compared detected sUAS activity with locations and altitudes prescribed by the FAA’s UAS Facility Maps. According to the FAA, “UAS Facility Maps show the maximum altitudes around airports where the FAA may authorize Part 107 operations without additional safety analysis.” More than 20 percent of the 177 flights were flying higher than the safe altitude prescribed for their operating area. Moreover, researchers compared detected UAS operations to historical manned aircraft flight data, revealing several near encounters."